Summary The allocate directive specifies how to allocate the specified variables. The allocate directive is a declarative directive if it is not associated with an allocation statement.
The syntax of the allocate directive is as follows:
#pragma omp allocate(list) [clause[ [,] clause] ... ] new-line
where clause is one of the following:
allocator(allocator)
align(alignment)
where allocator is an expression of omp_allocator_handle_t type and alignment is a constant positive integer expression with a value that is a power of two.
The syntax of the allocate directive is as follows:
!$omp allocate(list) [clause[ [,] clause] ... ]
!$omp allocate[(list)] [clause[ [,] clause] ... ]
[!$omp allocate[(list)] [clause[ [,] clause] ... ]
[...]]
allocate-stmt
where allocate-stmt is a Fortran ALLOCATE statement and clause is one of the following:
allocator(allocator)
align(alignment)
where allocator is an integer expression of omp_allocator_handle_kindkind and alignment is a constant scalar positive integer expression with a value that is a power of two.
Description The storage for each list item that appears in the allocate directive is provided by an allocation through a memory allocator. If no allocator clause is specified then the memory allocator specified by the def-allocator-var ICV is used. If the allocator clause is specified, the memory allocator specified in the clause is used. If the align clause is specified then the allocation of each list item is byte aligned to at least the maximum of the alignment required by the base language for the type of that list item, the alignment trait of the allocator and the alignment value of the align clause. If the align clause is not specified then the allocation of each list item is byte aligned to at least the maximum of the alignment required by the base language for the type of that list item and the alignment trait of the allocator.
The scope of this allocation is that of the list item in the base language. At the end of the scope for a given list item the memory allocator used to allocate that list item deallocates the storage.
If the directive is associated with an allocate-stmt, the allocate-stmt allocates all list items that appear in the directive list using the specified memory allocator. If no list items are specified then all variables that are listed by the allocate-stmt and are not listed in an allocate directive associated with the statement are allocated with the specified memory allocator.
For allocations that arise from this directive the null_fb value of the fallback allocator trait behaves as if the abort_fb had been specified.
Restrictions Restrictions to the allocate directive are as follows:
∙ If a list item has static storage duration, the allocator clause must be specified and the allocator expression in the clause must be a constant expression that evaluates to one of the predefined memory allocator values. ∙ A variable that is declared in a namespace or global scope may only appear as a list item in an allocate directive if an allocate directive that lists the variable follows a declaration that defines the variable and if all allocate directives that list the variable specify the same allocator.
∙ After a list item has been allocated, the scope that contains the allocate directive must not end abnormally, such as through a call to the longjmp function.
∙ After a list item has been allocated, the scope that contains the allocate directive must not end abnormally, such as through a call to the longjmp function, other than through C++ exceptions. ∙ A variable that has a reference type may not appear as a list item in an allocate directive.
∙ An allocate directive that is associated with an allocate-stmt and specifies a list must be preceded by an executable statement or OpenMP construct. ∙ A list item that is specified in a declarative allocate directive must not have the ALLOCATABLE or POINTER attribute. ∙ If a list item is specified in an allocate directive that is associated with an allocate-stmt, it must appear as one of the data objects in the allocation list of that statement. ∙ A list item may not be specified more than once in an allocate directive that is associated with an allocate-stmt. ∙ If multiple directives are associated with an allocate-stmt then at most one directive may specify no list items. ∙ If a list item has the SAVE attribute, either explicitly or implicitly, or is a common block name then the allocator clause must be specified and only predefined memory allocator parameters can be used in the clause. ∙ A variable that is part of a common block may not be specified as a list item in an allocate directive, except implicitly via the named common block. ∙ A named common block may appear as a list item in at most one allocate directive in a given compilation unit. ∙ If a named common block appears as a list item in an allocate directive, it must appear as a list item in an allocate directive that specifies the same allocator in every compilation unit in which the common block is used. ∙ An associate name may not appear as a list item in an allocate directive. ∙ A type parameter inquiry cannot appear in an allocate directive.